1. Field of the Invention
The present invention relates generally to a unified device for adjacent and non-adjacent channels/carriers for transmitting and receiving Physical layer Protocol Data Units (PPDUs), and more particularly, to a dual-use device capable of processing either 80+80 Megahertz (MHz) PPDUs with a single spatial stream (160/80+80 MHz 1×1) or 80 MHz PPDUs with two spatial streams (80 MHz 2×2).
2. Description of the Related Art
The IEEE 802.11ac standard (the Standard′) builds on the Multiple Input Multiple Output (MIMO) techniques introduced in the IEEE 802.11n standard (which is hereby incorporated by reference in its entirety), and specifies transmission of wide-band 80 MHz and 160 MHz bandwidth modulations. The 160 MHz transmissions occupy two 80 MHz channels that may be adjacent in frequency, in which case they are called 160 MHz transmissions or PPDUs, or non-adjacent in the case of ‘80+80 MHz PPDUs’.
Conventionally, the sub-carrier allocation is specified for 160 MHz channels so that it matches exactly that of two adjacent 80 MHz channels (i.e. with their center frequencies separated by 80 MHz), thus allowing the two 80 MHz parts of a 160 MHz or 80+80 MHz PPDU to be transmitted or received using two separate 80 MHz transceivers.
FIG. 1 illustrates a 2-antenna 80+80 MHz structure operating in a 2×2 MIMO configuration, to which the present invention is applied. In FIG. 1, the structure 100 includes a WiFi modem chip 110 incorporating a space-time stream #1 120 and a space-time stream #2 130 connected to two front-end circuits 160 and 170, respectively, through respective buffers 140 and 150. Specifically, for each space-time stream, a Transmission (Tx) Radio Frequency (RF) port enters the buffer and exits to the front-end circuit, and a Reception (Rx) RF port is received directly from each of the front-end circuits, which are connected to antennas 180. In FIG. 1, one oscillator is used to transmit or receive the 80+80 MHz modulation, as shown in FIG. 2, as both front-end circuits 160 and 170 operate on the same frequency.
Specifically, FIG. 2 illustrates a dual Local Oscillator (LO) structure for the 2-antenna 80+80 MHz structure illustrated in FIG. 1. The LO structure 200 in FIG. 2 includes two oscillators LO1 and LO2, which are connected in the space-time streams #1 and #2 in FIG. 1, respectively. The signal from LO1 is fed to a first Mixer (M1), where it is combined with the upper input stream and is output. Similarly, the signal from LO2 is fed to a second Mixer (M2), where it is combined with the lower input stream and is output.
As an alternative for the embodiment of FIGS. 1 and 2, the conventional art also teaches the use of one LO, as illustrated by LO1 in the single LO structure 300 in FIG. 3. The signal from LO1 is fed to both M1 and M2, where it is combined with the upper and lower input streams, respectively, and is output. The embodiment of FIG. 3, in which one oscillator drives both transceivers, has been proposed to mitigate possible interference between the two oscillators in the embodiment of FIG. 2.
However, the use of the two oscillators in the conventional art, in the manner of FIG. 2, causes switching difficulties when applying the signal to the two transceivers. In addition, users tend to possess a plurality of mobile units operating in various frequencies, yet the conventional art is deficient in providing one structure to accommodate a user's needs to operate in either frequency/spatial multiplexing configuration, and to reuse the same device in the various mobile units that the user may possess, through reconfiguration.
Accordingly, there is a need in the art for a reusable, unified device capable of processing either 80+80 Megahertz (MHz) PPDUs with a single spatial stream (160/80+80 MHz 1×1) or 80 MHz PPDUs with two spatial streams (80 MHz 2×2).